Natural Kinds and Concepts: a Pragmatist and Methodologically Naturalistic Account

Natural Kinds and Concepts: A Pragmatist and Methodologically Naturalistic Account Ingo Brigandt Abstract: In this chapter I lay out a notion of philosophical naturalism that aligns with pragmatism. It is developed and illustrated by a presentation of my views on natural kinds and my theory of concepts. Both accounts reflect a methodological naturalism and are defended not by way of metaphysical considerations, but in terms of their philosophical fruitfulness. A core theme is that the epistemic interests of scientists have to be taken into account by any naturalistic philosophy of science in general, and any account of natural kinds and scientific concepts in particular. I conclude with general methodological remarks on how to develop and defend philosophical notions without using intuitions. The central aim of this essay is to put forward a notion of naturalism that broadly aligns with pragmatism. I do so by outlining my views on natural kinds and my account of concepts, which I have defended in recent publications (Brigandt, 2009, 2010b). Philosophical accounts of both natural kinds and concepts are usually taken to be metaphysical endeavours, which attempt to develop a theory of the nature of natural kinds (as objectively existing entities of the world) or of the nature of concepts (as objectively existing mental entities). However, I shall argue that any account of natural kinds or concepts must answer to epistemological questions as well and will offer a simultaneously pragmatist and naturalistic defence of my views on natural kinds and concepts. Many philosophers conceive of naturalism as a primarily metaphysical doctrine, such as a commitment to a physicalist ontology or the idea that humans and their intellectual and moral capacities are a part of nature. Sometimes such legitimate views motivate a more contentious philosophical program that maintains that any philosophical notion ought to be defined in a purely physicalist vocabulary (e.g., by putting forward a theory of concepts and intentional states that does not define them in terms of intentional notions). We will see that I reject this latter project (which is naturalistic in some sense) on naturalistic grounds, as science does not aim at developing reductive definitions. Rather than naturalism as a metaphysical doctrine, more germane to my account is a methodological type of naturalism. Here the idea is that some aspects of scientific method and practice should be used by philosophers in their attempts to develop philosophical accounts. I will illustrate this naturalistic method by laying out how philosophers can and ought to develop philosophical notions without simply relying on their personal intuitions or folk intuitions as revealed by experimental philosophy surveys. The starting point of this method is that philoso172 Ingo Brigandt phical concepts are introduced for specific philosophical purposes – just like scientific concepts are used for particular epistemic purposes – and that these purposes determine the appropriateness of a philosophical analysis. For example, I will defend my account of what a ‘concept’ is in terms of its fruitfulness for explaining phenomena of interest to philosophers. My methodological naturalism aligns with a pragmatist perspective, since science is to a large extent a pragmatic enterprise and since scientists freely invoke scientific values and interests and defend their accounts in terms of their fruitfulness at meeting scientific aims. Natural kinds The traditional philosophical aim of an account of natural kinds is to provide a metaphysical characterisation of what a natural kind is, which among other things distinguishes natural kinds from other kinds and entities (Bird and Tobin, 2009). Given that, broadly speaking, a natural kind is a grouping of objects that corresponds to the objective structure of nature, an account of natural kinds must explain how natural kinds differ from nominal kinds, i.e., a grouping of various objects that is merely the result of human convention. One possibility is to define natural kinds as those kinds that figure in laws of nature (Fodor, 1974). Another, though not necessarily conflicting account may construe a natural kind as characterised by an essence, i.e., some intrinsic, structural property that all kind members share and that causes the typical properties associated with the kind (Putnam, 1975). For instance, the essence of oxygen is its atomic structure, including the number of subatomic particles making up an oxygen atom. This atomic structure explains in which chemical reactions oxygen can participate, and other chemical properties characteristic of the natural kind oxygen. Functional kinds are generally considered to not be natural kinds; for if kind membership is defined by members having a common function, such a kind is bound to be structurally heterogeneous. This is because any one function is multiply realizable, i.e., there are different actual or possible physical entities that realize this function in one way or another. For instance, instances of ‘money’ as a functional kind include different metals (gold, coins), different objects made of paper (bills, cheques), and electronic states and information (computerized bank accounts). A functional kind from ecology such as ‘predator’ is likewise multiply realized. There is a plethora of predatory species across the animal kingdom that differ substantially in their structural-anatomical, physiological, developmental, and even behavioural properties. The structural heterogeneity of functional kinds is usually considered to be incompatible with them being natural kinds, which are deemed to be characterized by a shared structural essence. Natural Kinds and Concepts 173 Yet a look at biology suggests that many natural kinds are heterogeneous. A case in point is species and higher taxa, which have been taken to be prime examples of natural kinds in biology. The different individuals forming a biological species (e.g., orangutans) or a higher taxon (e.g., vertebrates) can be very different from each others. This variation is a biological reality and of scientific importance (e.g., underwriting the ability of species to evolve), so heterogeneity need not be an accidental feature, but can be constitutive of some kinds (Wilson et al., 2007). A good metaphysical solution is to make use of Richard Boyd’s (1991, 1999a, 1999b) suggestion that natural kinds are homeostatic property clusters (HPC kinds). The identity of an HPC kind is, in general, not determined by a single essential property; instead, there is a cluster of properties that are correlated. Most of the kind members possess most of these properties, but none of the properties in the cluster has to be shared by all kind members, permitting variation among the members of an HPC natural kind. A requirement is that the correlation of properties is not an accident, but due to some mechanisms that causally maintain the correlation (thus the label ‘homeostatic’ property cluster). Thereby our grouping of objects into a kind based on such a cluster of correlated properties conforms to features in nature and HPC kinds are indeed natural rather than nominal kinds (Wilson et al., 2007). Given the possibility of heterogeneous natural kinds, one may wonder whether at least some functional kinds are natural kinds after all. One option is to try to assess how many properties are correlated in a given kind, and count those kinds as natural where a sufficient number of properties are correlated. However, this approach ultimately results in a continuum between nominal kinds and natural kinds. More importantly, simply counting the number of properties correlated (or assessing the degree of homogeneity) fails to pay attention to the crucial epistemic role that natural kinds have for science. Natural kinds are important because they permit induction and explanation. In his discussion of the problem of induction, Nelson Goodman (1955) prominently argued that reliable induction requires projectible predicates. Within a contemporary, realist framework (which I adopt), it is clear that a predicate referring to a natural kind is projectible. The reliable correlation of properties in an HPC kind, for instance, grounds induction and other instances of scientific inference. Many natural kinds support scientific explanations, e.g., if the kind figures in laws or if the kind’s essence (or one of the properties from the cluster defining an HPC kind) causes some of the features typically associated with a kind. As I have argued in a previous paper, illustrated by biological examples (Brigandt, 2009), the above considerations suggest that the main philosophical task is not to offer a metaphysical construal of what a natural kind is, but an epistemological study of (i) what inferential and explanatory aims scientists pursue with the study of a certain natural kind, and (ii) how well a grouping of ob174 Ingo Brigandt jects into a kind meets such inferential and explanatory aims.1 For also many functional kinds studied for instance in ecology, physiology, psychology, or economics figure in scientifically important generalizations and explanations. While ‘money’ is multiply realized, it is part of many macroeconomic generalizations, such as Gresham’s law. Ecological generalizations exist for the temporal change of the sizes of predator and prey populations. Such generalizations do not describe internal, structural aspects of the members of a functional kind (e.g., organisms from different predator species), instead, the generalization pertains to relations between members of a functional and other kinds (e.g., predators from one species and their prey species). While the essences of natural kinds have typically been assumed to be intrinsic properties, relational properties are also important for many natural kinds from biology. A higher taxon (e.g., vertebrates) is defined as consisting of those organisms that are descended from a specific ancestral species, and ‘being descended from’ is a relational property. Likewise, many species concepts define a species in terms of relational properties, such as the ability to interbreed with other species members. This is why the HPC construal of kinds explicitly permits the cluster of properties that characterizes a natural kind to include both intrinsic and relational properties (Brigandt, 2009). Many biological entities (e.g., in molecular biology and physiology) possess their causal capacities only in certain contexts, so that biological explanations often involve relational properties (Brigandt, in press). Internal structure and structural homogeneity is not at all the only way to ground generalizations and explanations. Many functional kinds support scientific generalizations and explanations, and thereby meet an epistemic hallmark of natural kinds. Debating whether or not some functional kinds really are natural kinds – based on some metaphysical construal of natural kinds – is moot. For any kind, the philosophically relevant question is an epistemic issue: how scientifically important is the grouping of an object into a kind, i.e., what generalizations and explanations can the kind figure in, and how important are they? This cannot be assessed in terms of how ‘natural’ or ‘real’ a grouping of objects is, or by simply counting how many properties are co-instantiated in a kind. Boyd (1999a, 1999b) – who I follow on this issue – has already highlighted the epistemic dimension of natural kinds by his notion of ‘accommodation’. The idea is that there are certain inductive and ex- <ul style="display: flex;"><li style="flex:1">1</li><li style="flex:1">Even a traditional essentialist construal of natural kinds hints at this. An essence has two </li></ul>functions: (1) It determines kind membership (exactly those objects possessing the essence are kind members), and (2) it accounts for the kind’s characteristic properties (e.g., by virtue of the essence causing those properties). But condition (1) alone cannot define the notion of a natural kind, as even the members of a nominal kind share a property, namely, being a member of this conventionally defined kind. For a property metaphysically determining kind membership to be the essence of a natural kind, condition (2) has to apply, which points at the epistemic issue of whether this property is causally relevant. Natural Kinds and Concepts 175 planatory demands in science, and a grouping of objects is a natural kind to the extent to which these objects possess properties that fulfil – accommodate – the inductive and explanatory demands. Boyd’s approach is naturalistic in that he puts forward a revised notion of ‘natural kind’ with the aim of capturing natural kinds as they are found in different scientific fields, including the special sciences. While the traditional construal of natural kinds as characterized by an intrinsic, structural essence applies to physico-chemical kinds only, kinds studied in biology, psychology, and the social sciences are nonetheless epistemically important by figuring in generalizations and explanations. In summary, I do not think that there is any clear-cut metaphysical boundary between natural kinds and other kinds, and furthermore, I think that a purely metaphysical construal of what a natural kind is is of very limited use. The important philosophical task is an epistemological account of the role and relevance of various kinds in scientific theorizing. My account is naturalistic in that my only overarching philosophical theory is that natural kinds have to be philosophically studied based on the empirical details pertaining to each kind. These empirical considerations may differ from case to case. Some kinds have traditional essences, others are HPC kinds; some kinds figure in inductions only, others support explanations. Even within a scientific subdiscipline such as molecular biology, there are both kinds characterized by intrinsic properties, while other kinds are defined by relational properties. Most importantly, the empirical considerations pertaining to a kind include not only empirical properties of the kind’s members, but also the epistemic-scientific aims that can be met by using the kind in scientific theorizing. These features matter for scientific practice and theory, so that a naturalistic approach must take them into account. The philosophical task ought to be a study of (i) what inferential and explanatory aims scientists pursue with the study of a certain natural kind, and (ii) how well a grouping of objects into a kind meets such inferential and explanatory aims (Brigandt, 2009; see also Love, 2009). In addition to being naturalistic, this account of natural kinds is pragmatist as it essentially includes the goals of intellectual activity. I adopt a realism rather than an anti-realism about kinds in that it depends on the actual structure of the world whether the properties of kind members permit successful inference and explanation. At the same time, whether a kind is scientifically important (deemed a ‘natural’ kind) depends on what our inferential and explanatory interests are. The ineliminable role of human interests and values has been a core theme for several 19th and especially 20th century pragmatists; and I have argued that intellectual interests are relevant even for an account of natural kinds, which has traditionally been considered a purely metaphysical issue. I do not think that there is a unique representation of or classification scheme for the world, for there are various theoretical or intellectual goals that we (not nature) have, and different classifications or groupings into kinds may be needed to meet different 176 Ingo Brigandt goals (Dupré, 1993). My account of natural kinds is not defended by reference to metaphysical considerations (such as a clear and principled distinction between natural kinds and other kinds); rather, I defend it in terms of its fruitfulness for understanding how natural kinds figure in scientific theorizing – a genuinely philosophical question. Scientific concepts This section lays out a theory of concepts, which I originally developed in recent writings (Brigandt, 2006, 2010b). The main motivation of this theory is to account for the rationality of semantic change, and I illustrate my framework by applying it to two cases of conceptual change in biology – the homology concept and the gene concept. A later section will discuss how I defend this account of concepts and draw implications for naturalism and pragmatism. On my account, a scientific concept consists of three components of content: (1) the concept’s reference, (2) the concept’s inferential role, and (3) the epistemic goal pursued by the concept’s use. There are two reasons for recognizing these three components. First, the different components of content (or different semantic properties of scientific terms) are ascribed for and fulfil different philosophical functions. Second, in the course of history a scientific concept may change in any of these components (and one component can change without the others). It should be obvious why I follow the tradition in considering reference to be part of a concept’s content. Since two coreferential concepts may have a different epistemic role, philosophers often recognize a concept’s sense or intension in addition to its reference. My version of this additional component is the concept’s inferential role (as defended by inferential role semantics, also called conceptual role semantics). A term’s inferential role is the set of inferences and explanations in which the term figures and which it supports in virtue of its specific content. The inferential role broadly aligns with the definition of a scientific term. Central biological concepts may change in the course of history and their use may vary across different scientists, which is more precisely change or variation in a concept’s inferential role and possibly its reference. I introduce the novel notion of the epistemic goal of a concept precisely because it accounts for the rationality of semantic change and variation. It is well-known that scientists pursue various epistemic goals; scientists aim at discovering different phenomena, making scientific inferences and confirming generalizations, and explaining various processes. A particular epistemic goal (e.g. explaining cell-cell communication) is often specific to a certain scientific field, in that it is pursued by this field (or a class of related fields), while other fields pursue other epistemic goals. Typically, many scientific concepts are deployed to pursue a given epis- Natural Kinds and Concepts 177 temic goal. My point here is that there are cases where an epistemic goal is tied to a specific scientific concept, in that the very rationale of introducing this concept and of continuing to use it is to pursue the epistemic goal. For example, the concept of natural selection is used to account for evolutionary adaptation. Some biological concepts are not used for any explanatory or deep theoretical purposes, but for the epistemic goal of discovering certain phenomena, as with some concepts from molecular and experimental biology. The below accounts of the homology concept and the gene concept will illustrate this idea in concrete cases. In a nutshell, the epistemic goal pursued by a scientific concept’s use is the type of knowledge (certain kinds of inferences, explanations, discoveries) the concept is intended to deliver, given its usage by a research community.2 (The inferential role, in contrast, is the set of inferences and explanations that the concept currently actually supports.) A concept – or more precisely, its inferential role – embodies beliefs about the concept’s referent. While scientists constantly acquire novel beliefs or discard previous ideas about the term’s referent, these revised beliefs usually do not lead to a redefinition of the term under consideration. Thus, what has to be accounted for in the case of semantic change is why certain novel beliefs about a term’s referent (but not others) warranted a change in the very inferential role (sense) of the term. On my account, the epistemic goal pursued by a term’s use sets the standards for which possible changes in the term’s inferential role count as rational. For instance, a concept’s epistemic goal may be to explain certain phenomena, yet presently the concept’s definition – reflecting available empirical beliefs – does not yield an adequate explanation of this kind. Once appropriate empirical insights become available, the concept’s definition (inferential role) is revised, and this semantic change is warranted if in virtue of the new definition the concept supports the desired explanation. In general terms, change in a term’s inferential role is rational if the new inferential role meets the term’s epistemic goal to a higher degree than the term’s prior inferential role. If rational change in inferential role entails a change in the term’s reference, the latter is also rational. Sometimes, within a scientific discipline there is some variation even in the epistemic goal for which a term is used. This variation in the purposes for which a concept is used accounts for semantic variation, i.e., variation in the concept’s inferential role and possibly its reference. While I introduce the notion of epistemic goal to account for the rationality of semantic change and variation, the traditional conceptual components of reference and inferential role are needed for a different purpose, namely, to account for how concepts make successful practice (verbal behaviour and interaction with the world) possible. <ul style="display: flex;"><li style="flex:1">2</li><li style="flex:1">I do not maintain that an epistemic goal can be assigned to every scientific concept. As </li></ul>the notion of epistemic goal is to account for semantic change and variation (which usually only major theoretical concepts exhibit), it is sufficient to ascribe it to those concepts where semantic change or variation occur. 178 Ingo Brigandt The change of the homology concept Homology is a concept central to the practice of comparative and evolutionary biology (Brigandt, 2006; Brigandt and Griffiths, 2007). Homologous structures are the corresponding structures in different species. For example, the right arm in humans, the right forelimb in horses, the right flipper in dolphins, and the right wing of bats are homologous. Even the individual bones of the right forelimb (e.g., radius and ulna) reoccur in different species. Homologous structures are considered the same structures and given the same name in different species. Apart from bones, all sorts of anatomical structures can be homologous, such as organs, individual muscles, nerves, and tissues. Cell types and molecular structures such as genes are also considered homologous across species. Homologous structures are present in different species due to inheritance from the species’ common ancestor. This yields the post-Darwinian definition of homology: two structures in different species are homologous if they are derived from the same structure in the ancestor. Despite the evolutionary nature of homology, the homology concept was introduced at the beginning of the 18th century and was already an important concept in comparative biology well before the advent of Darwin’s theory of evolution. In this pre-Darwinian period different non-evolutionary accounts were given for homologous structures. One idea was that different species are governed by the same laws of development, resulting in corresponding structures in different species. Another account appealed to abstract geometric body plans (or possibly to blueprints in the mind of God), so that structures in actual species were defined to be homologous in case they corresponded to the same element in the abstract body plan. This change in the definition of homology is an instance of semantic change, and it raises the following worry: Does the Darwinian revolution amount to the replacement of the pre-Darwinian concept of homology by a different concept, so that the term ‘homology’ switched from one to another concept? Are the pre-Darwinian and post-Darwinian concepts of homology incommensurable (meaning incommensurability in the sense of Kuhn, 1962 and Feyerabend, 1962)? The same issue has been raised by philosophers in a related context, namely, the concept of ‘species’ (Beatty, 1986). Are the pre- and post-Darwinian accounts of the nature species two distinct concepts? This opens the (philosophically unsatisfactory) possibility of arguing that what Darwin’s Origin of Species actually showed was that there are no species – as defined by the pre-Darwinian concept of species. To return to the homology concept, some semantic change did occur with the advent of evolutionary theory. Specifically, what I refer to as the concept’s inferential role changed. However, there was also an important element of conceptual continuity, for the epistemic goal pursued by the use of the homology concept did not shift in the transition to Darwinism. Already before the advent of evolutionary theory, biologists used the homology concept for two epistemic

Natural Kinds and Concepts: a Pragmatist and Methodologically Naturalistic Account

Details

Download

Copyright

We respect the copyrights and intellectual property rights of all users. All uploaded documents are either original works of the uploader or authorized works of the rightful owners.

Support